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Seabed environments and shallow geology of the Leveque Shelf, Browse Basin, Western Australia - Chlorophyll a, b, and c and
phaeophytin a of seabed sediments.

Citation

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Abstract

Geoscience Australia undertook a marine survey of the Leveque Shelf (survey number SOL5754/GA0340), a sub-basin of the Browse
Basin, in May 2013. This survey provides seabed and shallow geological information to support an assessment of the CO2 storage
potential of the Browse sedimentary basin. The basin, located on the Northwest Shelf, Western Australia, was previously identified
by the Carbon Storage Taskforce (2009) as potentially suitable for CO2 storage. The survey was undertaken under the Australian
Government's National CO2 Infrastructure Plan (NCIP) to help identify sites suitable for the long term storage of CO2 within
reasonable distances of major sources of CO2 emissions. The principal aim of the Leveque Shelf marine survey was to look for
evidence of any past or current gas or fluid seepage at the seabed, and to determine whether these features are related to
structures (e.g. faults) in the Leveque Shelf area that may extend to the seabed. The survey also mapped seabed habitats and
biota to provide information on communities and biophysical features that may be associated with seepage. This research, combined
with deeper geological studies undertaken concurrently, addresses key questions on the potential for containment of CO2 in
the basin's proposed CO2 storage unit, i.e. the basal sedimentary section (Late Jurassic and Early Cretaceous), and the regional
integrity of the Jamieson Formation (the seal unit overlying the main reservoir). This dataset comprises total chlorin concentrations
and chlorin indices from the upper 2cm of seabed sediments.

Date (publication)

Product Type

Topic Category

Keywords

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound

-15.45

East bound

121.75

West bound

121.1

South bound

-16.1

Lineage

Bottom sediments were collected using either a Smith Macintyre grab or a Shipek grab. 0.4 ml samples of surface sediment (0-0.5
cm) were syringed into plastic bags. The samples were wrapped in Al foil and frozen. Chlorophyll concentrations were calculated
on sediment extracts (90% acetone + 0.1% MgCO3) at spectrophometric readings at wavelengths of 647, 630, 750 and 664 nm. For
chlorophyll-a (Chl-a) and phaeophytin-a, wavelengths of 664 nm and 750 nm (before and after the addition of 200 -L-1 0.1 mol
L-1 HCl per 2 mL extractant) and the equation derived by Lorenzen (1967) were used. Chlorphyll b and c concentrations were
calculated according to equations provided by Jeffrey and Welschmeyer (2003). The reproducibility of the measurements is +/-10%.
Lorenzen, C. J. (1967). Determination of chlorophyll and pheopigments: Spectrophotometric equations. Limnology and Oceanography
12, 343-346.
Jeffrey, S.W., and Welschmeyer, N.A. (2003). Spectrophotometric and fluorometric equations in common use in oceanography.
In 'Phytoplankton pigments in oceanography: guidelines to modern methods' (Eds. S.W. Jeffrey and R.F.C. Mantoura, and S.W.
Wright.) pp. 597-615. (UNESCO Paris.)
Thanks to the crew of the RV Solander for help with sample acquisition.